HKMG Gate Stack Barrier Layer for Multiple-Vt Aluminum Diffusion Control
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Solution Overview
Problem
As semiconductor technology advances, the challenge of achieving multiple threshold voltage (Vt) designs in integrated circuits becomes complex due to the limitations of gate length scaling and the need for effective gate metal materials, particularly in high-voltage devices where aluminum diffusion barriers are required.
Innovation Solution
A method for forming semiconductor structures using an HKMG process that involves forming FET devices with different nitrogen concentrations in barrier layers to create N-containing barrier layers, which are formed through in-situ and/or ex-situ nitridation, allowing for effective aluminum diffusion control and meeting multiple-Vt requirements while maintaining competitive gap-filling abilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-k gate dielectric layer is used to reduce gate leakage, then the effective dielectric thickness is improved, but aluminum diffusion into the gate dielectric layer occurs
Solution Approach 1:
A barrier layer is introduced as an intermediary between the work function metal layer and the high-k gate dielectric layer. This barrier layer prevents aluminum diffusion from the work function metal into the high-k gate dielectric, while allowing the high-k dielectric to maintain its gate leakage control functionality. The barrier layer acts as a mediator that resolves the conflict between using high-k materials and preventing metal diffusion.
Solution Approach 2:
The gate stack is structured as a composite material system consisting of multiple layers: high-k gate dielectric layer, barrier layer, and work function metal layer. Each layer serves a specific function, and their combination creates a structure that simultaneously achieves gate leakage control, aluminum diffusion prevention, and proper work function characteristics.
2Productivity
If the gate length is scaled down to improve device performance, then the transistor density is improved, but the complexity of the manufacturing process increases
Solution Approach 1:
The gate structure is segmented into multiple functional layers (high-k gate dielectric layer, barrier layer, work function metal layer) that can be formed using separate process steps. This segmentation allows each layer to be optimized independently for its specific function, enabling scaled dimensions while managing manufacturing complexity through modular process design.
3Reliability
If a barrier layer is added to prevent aluminum diffusion, then the barrier performance is improved, but the gap-filling ability deteriorates
Solution Approach 1:
The barrier layer parameters (thickness, material composition) are optimized to achieve the right balance between aluminum diffusion barrier performance and gap-filling ability. By adjusting these parameters, the barrier layer can provide sufficient protection against aluminum diffusion while maintaining adequate conformality and filling characteristics for the gate structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively mitigates aluminum diffusion into high-k gate dielectric layers, enabling the creation of semiconductor structures suitable for multiple-Vt designs with improved barrier performance and reduced impact on gap filling, suitable for both high-voltage and low-voltage devices.
Implementation Method 1
increasing a nitrogen (N) concentration in the barrier layer by an in-situ treatment and/or an ex-situ treatment
Data Source
AI summary
A semiconductor structure includes a first metal gate structure and a second metal gate structure. The first metal gate structure includes a first high-k gate dielectric layer, a first work function metal layer over the first high-k gate dielectric layer, and an N-containing barrier layer between the first high-k gate dielectric layer and the first work function metal layer. The second metal gate structure includes a second high-k gate dielectric layer and a second work function metal layer over the second high-k gate dielectric layer. The first high-k gate dielectric layer and the second high-k gate dielectric layer include a same metal material. The first high-k gate dielectric layer has a first metal concentration, the second high-k gate dielectric layer has a second metal concentration, and the first metal concentration is less than the second metal concentration.